There is a conventional digital content distribution system that uses DRM (Digital Rights Management) technology (refer to Patent Document 1). DRM technology enables usage restrictions relating to the number of playback times, transfer, duplication, and so forth to be set for distributed content.
Also, there is a conventional digital content distribution system that uses metadata stipulated by the TV-Anytime forum. According to the method stipulated by the TV-Anytime forum, the contents of a specific section of content (such as a CM, the first inning of a baseball game, or the first half of a soccer match) are described by means of segmentation metadata.
In recent years, the increased capacities of HDDs installed in PVRs (Personal Video Recorders) and an automatic recording function have made it possible for a program to be recorded automatically and viewed by the user later. However, since special playback such as 30-second skipping, fast-forwarding, and jumping to a specified time can be freely used in recorded viewing, CMs are frequently skipped when a program is viewed, and the current CM business model in real-time broadcasting is becoming nonviable.
Also, even if it is wished to apply a broadcasting type of CM business model to content downloaded via an IP network, it is difficult to implement this since special playback can be freely performed with a playback player. However, in solving these problems, even though the number of times content is played back can be restricted by means of conventional DRM technology, there is no way of restricting the playback method, such as special playback. Furthermore, although it is possible to describe a specific section of a program as a CM section by means of segmentation metadata, there is no way of restricting special playback and so forth only for that section.    Patent Document 1: Unexamined Japanese Patent Publication No. 2002-342518